Paper Heart
by Pear Holiday
Summary: Somewhat AU. Up until this point, the only man that Kotoko had known was him. And Naoki had never been good at sharing. Rated M for sexual situations. Oneshot.


**Author's Note:** Hi, everyone! Thanks for reading.

A few things worth noting: Kotoko and Naoki have known each other from childhood. There are also mentions of an underage character exploring their sexuality on their own, and depictions of sex. So if that's not your cup of tea, move along. YOU'VE BEEN WARNED.

 **This story is also on my Archive Of Our Own account, which you can find on my profile!**

* * *

 **Disclaimer:** Itazura na Kiss, or any of its characters, do not belong to me and never will. Sob.

* * *

Kotoko Aihara had been a part of Naoki Irie's life for as long as he could remember. As try as he might, he couldn't recall a time in his life when she had not been a part of his life. In fact, if he had been a lesser, more dense mortal, he probably would have been convinced that Kotoko's mother had birthed Kotoko right alongside his own mother, while she had been in labor herself.

His first memory was of the two of them playing house in his front yard during an autumn day. His mother had been busy preparing snacks for the two of them in the kitchen, and Kotoko was busy collecting sticks for her makeshift "spaghetti," as the mommy. Naoki had done his share as the daddy by finding a big, flat rock from his mother's garden (which she probably wouldn't be happy about) to plate the "spaghetti."

And after the two of them had shared the meal, he'd kissed her on the mouth like he saw his father often do to his mother, and had tucked Kotoko and himself under a pile of leaves to "go to sleep."

Foolish Kotoko had actually fallen asleep under the leaves, but Naoki couldn't help but smile. Isn't that what mommies and daddies were supposed to do, anyway? Sleep next to each other? Kotoko was just getting into the role, he supposed.

He took a real bite of a twig resting on the large flat rock, and spat it out. She could be a lovely wife, maybe, but her spaghetti was terrible.

* * *

"Hey, Irie-kun, let's play mommies and daddies," a seven-year-old Kotoko had said, twisting her hair around her finger, not meeting his eye.

"That's for babies. We're not kids anymore." Naoki retorted, not even bothering to look up from his book. "Stop being an idiot."

Kotoko's eyes welled up with tears. "I… but… I like you, Irie-kun! I want to be a mommy and daddy with you!"

Naoki had flipped the page of his book. "First of all, the correct way to say that sentence would be, 'I want to be married to you.' Geez, you're such an idiot. When are you going to grow…"

Naoki never had a chance to finish that sentence, because Kotoko had poured her glass of milk over his head. So of course, when she ran home, he didn't chase her.

But she was back the next day, to his mother's overflowing joy, smiling as if nothing had ever happened. Naoki, who had never been one to let go of a good grudge, had not even acknowledged her presence.

"Irie-kun, I want to be married to you!" she said suddenly.

Naoki rolled his eyes. "Che. As if I'd get married to someone as dumb as you." He had cringed them, fully expecting another milk-bath.

But Kotoko just bit her lip, trying her best to smile, while her eyes filled with tears.

"I know."

* * *

When Naoki was thirteen, his friend showed him a clipping from an erotic magazine that he'd stolen from his older brother. He didn't understand the sudden tightness at his groin, the sudden increase in his heartbeat. He had gone to the bathroom to take care of the issue, thinking that he had to pee it out, but it was different. But not in a bad way. And he wanted to feel that again.

So he waited until everyone in the house was sound asleep to take his shower that night. He re-imagined the clipping that he had seen at school – a girl, her supple breasts looking as if they'd burst out of the tiny bikini top, her legs spread to expose the moist spot on her bikini bottoms, her eyes half-lidded, her mouth slightly open. He found that touching himself somehow expedited the experience, and so he found himself experimenting: slow strokes at first, feeling electric, gaining momentum, leaving him on his knees, until he'd lost himself again. He felt as if he should be ashamed, but decided that he didn't want to cloud the pleasure he felt with an emotion so beneath him. He washed the white secretions down the drain.

However, as weeks passed, he found that re-imagining that magazine clipping didn't do it for him anymore. The girl that he had once found so erotic seemed so dull and predictable.

He'd looked around in school the next day to see if any girls at his school would do it for him. However, as much as he tried to fantasize the girls from his school in erotic positions, nobody he saw had him feeling as taut and liberated as that girl from the magazine made him feel.

So he decided to do some research of his own on his computer at home, to find some images that would help stimulate his fantasies. He had closed the door behind him, just in case.

While he was neck-deep in his salacious research, he'd heard a plate drop and shatter behind him.

"Irie… kun? What are you…" Naoki quickly turned around to see Kotoko on her knees, having lost her footing in her shock.

The delicious fear in her eyes and her slightly ajar lips burned into his mind. He knew, then, that she would do.

She would do just fine.

But first, he'd have to take care of the idiot's injuries.

* * *

The first time that the two of them had had sex, Naoki had walked in on an eighteen-year-old Kotoko masturbating, on the night that he'd kissed her at their class's graduation party.

"Hey, Kotoko, the bath is…" his words faltered, as he dropped his towel onto the floor.

Before him, Kotoko lay on her bed, her panties at her thighs, with three of her fingers still inside her, her face flushed. A sheen of sweat glistened over her breasts, unhindered by a bra.

Naoki had closed the door behind him and locked it, which was when Kotoko actually realized that he was in the room with her. She was unable to emit any noise from being rendered entirely shocked.

Rushing to pull her panties back on, she had pulled her fingers out from inside her. But before she'd realized it, Naoki had pinned that same hand down as he sat down beside her.

He had a dangerous look in his eyes that she had never seen before. "What were you doing… Ko. To. Ko?"

"I… I…"

His eyes glinted through his messy wet hair, as he moved to pin her down with his body against her bed. "And here, I thought you were a good little girl."

Kotoko's face flushed, and turned away from Naoki's. "What... what are you doing?" As he was only clad in his boxers, his bare chest pressed against Kotoko's breasts.

Naoki pressed his lips against Kotoko's neck. "Weren't you thinking about me? I could've sworn that I heard you say my name through the door."

He hadn't. But even in moments like these, he loved teasing her. Her deepened blush, however, affirmed that his suspicions had been correct.

He'd eventually had three of his fingers enter her that night, as she mewled for pleasure beneath him. She'd come undone as he finger-fucked her viciously, grabbing onto the bedpost as a means of support. Then, she'd taken him in her mouth and swallowed every last drop down.

There were no emotions exchanged – just raw emotion.

Or so he'd thought.

* * *

"Just because we fucked doesn't mean anything, you know." Naoki murmured to Kotoko, on their first day of college, when she'd insisted on clinging to his arm.

At that, she'd readily relinquished her grip, but her steps had slowed down.

Irritated that she was falling behind, he looked back, opening his mouth to speak. But when he turned around, he saw that he was alone.

Where had she gone?

* * *

The second time they'd had sex, it was after the day that Naoki had gone on a date with Matsumoto.

"Hey, Irie-kun…" Kotoko said, while the two of them were drying off by the edge of the pond from having fallen out the boat they'd been rowing. "I knew it. You're more into the Matsumoto type, right? Beautiful, big breasts, great legs…" Kotoko trailed off, staring off into the distance.

Perhaps she had been imagining herself with Matsumoto's body, wondering how differently her life could have played out then.

She hugged her knees to her chest, staring out at the water. No more people were rowing boats due to it already being sunset. The park would probably be closed soon.

"Hey, Irie-kun… it's getting late, so we-"

How many years had she called him "Irie-kun," already? She was on first-name basis with all of her friends, except him.

Unless she didn't consider him as a friend?

Well, what did it matter, anyway? She was an idiot.

Naoki gave her an irritated look before taking his shirt and pants off. Thinking that he was going to change out of his wet clothing, she covered her eyes out of courtesy.

And embarrassment.

But the next thing she felt was the softness of the grass against her back, with her wrists pinned under Naoki's large, warm hands.

She could feel his hardness against her belly, and swallowed hard.

And just as before, she relinquished control.

* * *

The third time that they'd had sex, it was Kotoko's first time sleeping in the same bed as Naoki, at his apartment.

The two of them had discussed their futures; how Naoki had decided to pursue his dream of becoming a doctor, and how Kotoko had subsequently decided to become a nurse. Naoki had Kotoko to thank for discovering something that he was actually passionate toward for the first time in his life.

But appreciation was not what left his mouth.

Instead, it was something he knew was cruel to say.

Naoki rolled on the bed so that he was face-to-face with Kotoko. "Pfft… I'm lying in bed right next to you, and I don't feel a thing."

He knew that he was hurting her, but he couldn't stop himself. Why was it always that way when it came to Kotoko?

Why was he always trying to protect himself from the best thing that had probably ever happened to him?

He expected tears, or a protest. But Kotoko didn't reply with words. She chose a simple gesture, instead: a firm kiss, on his forehead.

Something about that simple gesture set him off, and he found himself ripping his own clothes off Kotoko, his mouth kissing every inch of skin but her lips.

He had pulled off her plain cotton panties, tossed them aside so that she'd hopefully have trouble finding them, and had lapped up the nectar between her thighs. Just as she was about to come, he had thrust himself inside of her. He relished the tightening of her insides around him as she whispered his last name.

And he'd continued thrusting, sucking on the nape of her neck as he took her from behind. Her breasts hung from below her like ripened fruit, and he palmed them greedily as he rode out his pleasure.

The two of them had collapsed into the bed, him still inside of her, as he held her close to his chest.

But when Naoki woke up in the morning, all that was left of Kotoko was a hot cup of coffee awaiting him on his bedside table.

* * *

Twenty-two-year-old Kotoko had just come back from a date with Keita Kamogari from the nursing department.

Naoki had been waiting for her at the train station. It had been fairly easy for him to figure out where she'd be exiting, since he had secretly followed the pair all day.

He couldn't believe it – Naoki-motherfucking-Irie, the most beloved and brilliant medical intern at Tonan University Hospital for as long as anyone could remember – was stalking his ex-stalker-slash-childhood-friend on her date.

What the fuck was wrong with him?

No, what the fuck was wrong with her? How could she proclaim her love for him countless times, fuck him three times, and then run off to another man?

Kotoko had finally emerged from the station, and Naoki stood in front of her, irate. He opened the umbrella he had brought, and the two of them walked in silence all the way home.

Murmuring a thanks, Kotoko climbed up the stairs and went into her room.

Then, he could stand it no longer. Thank god nobody else had been home, or he would've woken everyone up with his angry stair-climbing.

"Kamogari? Are you fucking kidding me?" he finally spat out, after having locked Kotoko's bedroom door behind him.

Kotoko, who had been in the middle of changing, stood in front of her mirror in just her underwear. Her eyes filled with tears, but she didn't reply.

She grabbed her robe, wrapped it around herself, and sat down at her desk.

Naoki followed her, and slipped the robe off her shoulders. Kotoko sat in the chair, unmoving. Then, he turned the chair around and grabbed her shoulders.

"Kotoko… what happened to you?"

Kotoko looked downward. "I'm so tired, Irie-kun."

"Of what?" he demanded, grabbing her small face in his hand.

No. Stop, Kotoko. Please.

She met his gaze. "You just want to use me for my body. Because I'm here, and readily available."

She paused. "But Keita-kun doesn't. He actually cares about me, and he isn't afraid to show it. He doesn't just want to use me as his… fuck toy." She spat out.

Naoki froze. Somehow, those words sounded so wrong coming out of her mouth. His Kotoko's mouth.

He burned with the desire to have her see things his way; the fact that, it had just been her for him, all along. The fact that he'd been aloof to protect himself from getting hurt, not realizing just how deeply he had hurt her in the process.

"But you still love me." He almost begged.

He heard her tear fall onto her desk.

"So what? You don't love me. And maybe, Keita-kun…"

Fuck Keita-kun.

He felt himself moving. Then, to both their shock, he kissed Kotoko on the lips for the first time. She stiffened against him at first, but then melted against his lips, kissing him back.

Why the hell had he waited so long?

He pried her lips apart gently with his tongue, and her tongue shyly darted out to meet his. Then, lifting her up from the chair, he laid her on the bed gently as he continued to kiss her.

He broke the kiss off briefly, and took off his shirt and pants. Then, he looked at her eyes. They looked more alive, somehow. More alive than they had ever looked since they first time they had been together.

"Don't you dare talk about another man in front of me ever again."

She stared at him, wide-eyed.

"I love you, Kotoko."

Kotoko smiled, tears escaping her eyes. Pulling his head down toward herself, she kissed him.

"I've always loved you, Irie-kun."

He kissed her nose, and settled himself between her thighs. Rubbing his nose against hers, he smiled mischievously.

"You want me, don't you?" he said, rubbing his hardness coming to life through feeling her moisture through his boxers. "You need me inside."

When she didn't respond, he kissed her chin, then her neck, then her collarbone. This emitted a moan, and her legs shifted from under him.

He had never seen such an exquisite sight in his entire life.

"Tell me. I know you want me."

She didn't say a word, blushing furiously.

Naoki tried again. "You don't want Keita."

Kotoko didn't answer, still red.

"I guess you'll need some convincing, then."

Trailing his kisses downward, he gently licked her bellybutton. Then, he took his index finger and pushed it against her pursed lips. Without a word, she took it into her mouth and sucked. He pulled it out, eliciting another whimper, but he replaced his finger with his tongue as he took her mouth. The moistened finger, meanwhile, darted southward and teased her entrance. Kotoko arched her back with a sharp gasp.

Naoki pulled his index finger away, and used her wetness to moisten his middle finger. Then, the two fingers worked together to massage her nether region as his other hand palmed her small, firm breast. Kotoko moaned into his mouth, and Naoki could feel himself stiffening at the sound.

"Let's start with two for now," Naoki murmured, pulling away from her mouth. His two fingers glided inside. Kotoko let out a louder moan, arching her back and pressing her breasts against Naoki's face. Quick on the uptake, he took a nipple into his mouth and played with it with his tongue.

He could feel Kotoko growing wetter and wetter. "How about three?" he whispered into her ear, giving her earlobe a light nibble. Kotoko, having almost completely lost herself, managed to shake her head no, and reached for Naoki's boxers.

He hissed at her touch. God, it felt so good. Then, Kotoko took both her hands and pulled down his boxers. He lifted himself off her slightly to allow her remove them completely, and then settled himself between her thighs.

Upon his skin coming into contact with her thighs, she gasped and involuntarily spread her legs a bit wider. Naoki's breath hitched at his throat. He couldn't wait anymore.

As her response, she arched her hips upward to meet his hardness. Groaning, he grabbed his member and slid it into her, slowly. Kotoko dug her nails into his back, breathing hard.

"Kotoko, what's the matter?"

Kotoko shook her head, her eyes slightly wet. "Nothing, Irie-kun…"

He flicked her lip gently. "Stop that. Call me Naoki, already."

"Naoki… kun?"

And with that, he let himself sink into her. She clung tightly to him, becoming one with his body.

It was dizzying how tight she was. No matter which direction he moved, the only thing his brain could register was pure pleasure. He began slowly, teasing her by almost pulling out, and then slowly re-entering her. She began to relinquish her hold on his back, and lay with her arms at her sides. Still, her adorable face was marred with signs of pain.

Dipping his head down to her chest, Naoki took one nipple in his mouth while taking the other in between his fingers. At that, Kotoko's eyes closed gently and her mouth lay slightly ajar, allowing moans to escape.

Naoki pulled himself up and began rolling both her nipples in between his fingers, still fucking her. The bedframe began to shake slightly as the speed of his thrusts increased.

"Naoki… kun…"

"Don't you ever tell me that you're seeing another man, ever again. You're mine."

She nodded furiously, gasping.

"Say it." He growled, his hips slamming into hers.

Kotoko met his gaze with a desperate look in her eyes. "I'm… yours… Naoki-kun…"

He felt himself stiffening up as he let out a groan. He was so close to the edge. The bed creaked beneath them, with the headboard almost slamming against the wall.

Then, as much as it pained him to do so, he pulled out slowly.

Kotoko started getting up, protesting. "Why, Naoki-" but he shushed her with a kiss. Slowly, he made his way down her body with deep kisses placed on her neck, her collarbone, between her breasts, her rib, then her belly.

"Wait, Naoki-kun, what are you-" before she could finish her inquiry, he placed the softest kiss on the nest of hair at her nether region. Kotoko inhaled shakily.

Naoki shot her a satisfied smirk, and then began to work.

He placed both his hands on her thighs, ensuring that she wouldn't clamp her legs shut. Then, he took a finger, dipped it in the depth of her moistness, and traced around her outer lips slowly. Kotoko clenched the sheets beneath her, her body bucking at his touch.

He brought his mouth to her glistening entrance, and used his tongue to re-trace the path that his finger had just traveled. Kotoko could feel his hot breath against her entrance, and she shivered in pleasure.

Using two fingers, Naoki gently pried her folds apart to expose her inner folds, to see that she was sopping wet within. His eyes became hazy with lust.

Gently, Naoki placed the tip of his tongue near her entrance, and worked his way upward. He reveled in her taste, as he gave a gentle tap to her little bundle of nerves with his tongue. Letting out a cry, Kotoko lifted her hips toward Naoki's mouth to grant him better access.

"My, Kotoko. I didn't know you were such a dirty girl."

Years of enduring his teasing had implanted a sense of boldness into her. "I don't care. It feels… so good…" she murmured, grabbing his sandy locks.

Naoki felt the strain at his hips; a response to Kotoko's shamelessness.

He buried his head between her thighs, swirling his tongue around the core of her pleasure, flicking it occasionally. Moaning, Kotoko moved her hips to match his movements. Then, he rose for a moment, and inserted three fingers into her.

"Mmm… Naoki…" she breathed.

"My… quite forward, aren't you? You graduated from Irie-kun to just Naoki, without a suffix on my name, in a matter of minutes." he breathed against her wetness, as he sank his fingers deeper into her slowly.

"I… I…" gasped Kotoko, meeting his thrusts with her hips. He used his other free hand to spread her apart once more, and began caressing her pearl with his tongue. Naoki quickened his pace, thrusting faster and faster, eliciting a series of moans from Kotoko. At imagining what she'd looked like now – flailing about, at the mercy of his fingers and tongue – he could feel his pre-cum oozing out from his tip.

"Naoki… I… nnnnngh!" he could feel her hips sink back down to the bed, and her inner walls clenching against his fingers rhythmically. He pulled his fingers out slowly and kissed her thigh, before rising to take in the sight.

Kotoko, whose face glowed with post-orgasmic bliss, was looking up at Naoki with love in her eyes. Her breasts moved with each heaving breath, and her body twitched slightly with every wave of pleasure.

He gave her a quick peck on the cheek, and then flipped her over. Kotoko yelped, caught off guard.

"On your knees." He growled into her ear. "It's my turn now." His voice sounded dangerous, predatory. She obliged him, lifting herself up with her hands and knees.

He thrust into her easily, due to the lubrication that was a by-product of Kotoko's ecstasy. Holding himself upright by grabbing Kotoko's ass, Naoki thrust harder into her than he ever had. Kotoko struggled to keep her arms stiff from the sheer force.

An animalistic sound escaped Naoki as he let himself lose control, and he pounded into her from behind mercilessly. Kotoko's breasts swung back and forth madly. She moaned, enjoying the different level of fullness she felt at this angle.

Their hips moved in unison, building momentum together. Finally, Naoki's hands moved toward Kotoko's breasts, as he lay on her back. He was so close now.

He gently flicked her ear with his tongue, breathing raggedly. "Kotoko… I love you…"

Kotoko turned her head as far back as she could, with a small smile. "I love you too… Irie… no, Naoki."

Naoki felt a contraction at his groin, and then a release. Kotoko continued to move against him, milking his manhood. He rode out his orgasm inside her, thrusting helplessly.

Then, with a guttural moan, Naoki collapsed on top of Kotoko. Her arms finally gave way, and she found herself flattened against the bed by Naoki's body.

He rolled off of her slowly, breathing hard, and Kotoko turned to face him. She hesitantly reached toward him, but stopped.

Naoki reached toward her, and pulled her to his side. "What are you doing, idiot? No post-sex cuddles?" he murmured.

Kotoko's eyes widened. "But, you…"

"Shut up." He said, embracing her and burying his head into her shoulder. He could feel her reaching over to touch his back, gingerly.

Neither of them would have to keep count anymore.

* * *

 **Author's Note:** Hope you enjoyed it! Let me know what you think.


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